How to use a rope canister

Rope canisters and pop up buoys are in use across the industry with acoustic releases, how do Sonardyne recommend using our acoustic release kits with our rope canisters?

Here we will discuss our two favourite methods of using an RT 6-1000 with our rope canisters. However feel free to use these methodologies with your DIY rope canisters.

These methods are tried and tested across decades of Sonardyne being involved in shallow water releasing and mooring.

Method 1

This is Sonardyne’s preferred method whereby a RT 6-1000 and rope canister are not attached to the seabed structure.

The RT 6-1000 and rope canister are positioned vertically on the seabed and are not attached to the subsea asset. When released the flotation buoy will bring the RT 6-1000 and rope canister to the surface whilst spooling out rope. The subsea asset can then be retrieved by means of the rope.

The advantages and disadvantages of this method are shown below:

Advantages

• Rope will spool more efficiently so is less likely to get dragged out by tidal flow as it ascends
• Less likely to lose the transponder while recovering the asset
• If the current holds the transponder underwater the user will have confidence the release functioned correctly its position will change. The transponder can then be retrieved after waiting for slack water

Disadvantages

• Cannot position the subsea structure after transponder is released
• Flotation buoy can block acoustic transducer if mounted too close.
• Larger object so more possibility to drift in tidal flow

Method 2

This is an alternative method of using a pop up buoy and rope canister whereby the tope canister is attached to the seabed structure.

In this example the RT 6-1000 and rope canister are fixed to the structure. When released the flotation buoy brings the rope end to the surface leaving the RT 6-1000 and rope canister on the seabed. The subsea structure together with the RT 6-1000 and rope canister can then be retrieved by means of the rope.

Advantages

• Structure can still be tracked if the rope detaches
• Less buoyancy required

Disadvantages

• Flotation buoy can drift off in the tidal flow as it ascends dragging a long length of rope.
• Risk of transponder being damaged during recovery while dragging a large asset
• More complex buoy release method and risk of entanglement

Do you have any other ways of using our rope canisters and RT 6-1000 in shallow water? Or do you use deep water rope canisters and think we could update this page? If so, get in contact.

If you want more information, the methodologies here are covered in more detail in our manuals including how to rig up both of the examples discussed above.